The line system of an RO system must be decontaminated from time to time because otherwise organic deposits may settle in the interior of the lines and associated functional units, such as valves, etc., and it may be infested by germs that might be harmful to the health of patients treated by means of the dialysis devices. So far the line system of RO systems has been disinfected in practice with chemical agents or by hot cleaning. The hot cleaning process requires a huge amount of energy, and when chemical cleaning agents are used, one must make sure by taking utmost care that after decontamination there are no chemical residues remaining in the line system and its functional units.